An excess-current switch of this general type is known, for instance from Swiss Pat. No. 397 895. In this known excess-current switch, as in other similar, known excess-current switches (see German Pat. Nos. 1 072 717 and 1 134 149), a part is secured to the bimetallic strip which has a protruding holder nose for the end of one lever arm of the switching connector. This holder nose has an edge, with which an edge on the end face of the same lever arm of the switching bridge is associated. These two edges act as latching or releasing edges whenever the bimetallic strip, in the event of an excess current, deflects in the direction of a retraction of the holder nose away from the end region of the switching connector lever arm resting on the holder nose. Thus the position of the two associated latching edges relative to one another is the criterion for tripping the excess-current switch in accordance with the deflection of the bimetallic strip, or in other words in accordance with the magnitude and duration of the excess current.
A disadvantage of the known excess-current switches is that upon restarting or switching back on, at least one of the latching edges mentioned is mechanically stressed when, because of the actuation of the pushbutton and the attendant displacement of the switching connector, its end area on the end face that is to be locked into place slides over the holder nose of the bimetallic strip. The resulting increased wear on the latching edges thus impairs the timing constancy of the tripping characteristic of the excess-current switch. A further disadvantage is that in order to form the holder nose, a separate component must be secured to the bimetallic strip, which increases the expense of manufacture and may be the source of further inaccuracies.
In the known excess-current switches mentioned above, the button spring not only has the function of putting the pushbutton into a position corresponding to the OFF position of the switch, but also, via the switch rod, generates the contact pressure of the switching connector upon the fixed contact piece as well as the disconnection force acting upon the switching connector. This has the drawback that to turn the switch on, a considerable actuation force must be exerted upon the pushbutton, and that in the ON or circuit-closing position of the switch the contact pressure is dependent on the pushbutton position, which may vary, for instance if the pushbutton sticks or jams, or after repeated actuation of the pushbutton.
There is the additional disadvantage in the known excess-current switches that on switching the switch ON after one lever arm has locked into place behind the holder nose of the bimetallic strip, the switching connector pivots over the entire disconnection distance between its contact piece and the fixed contact piece, provoking harmful contact chatter.